This invention relates to roller assemblies for gravity and power roller conveyors and, more particularly, to a low-friction, self-lubricating, corrosion-resistant and contamination-resistant roller assembly especially useful in sanitary roller conveyor applications.
An important problem in the use of conveyor rollers in sanitary roller conveyor applications is the ability to prevent the buildup of contaminants such as food particles and the like in crevices and interiors of parts such as the rollers and support mechanisms. In order to prevent such contamination, the roller conveyors are frequently washed or steam cleaned which subjects them often to caustic and corrosion-inducing fluids and materials.
Of the many previously known roller assemblies for gravity and power roller conveyors, a few of the more recent structures have utilized organic, polymeric plastics to form both the rollers and the closure pieces for the ends of the rollers to rotationally support them. Although such conveyor rollers have been easier to clean, the use of organic plastic corrosive-resistant parts made from such materials has often reduced the load rating of such conveyor rollers as compared to prior all-metal or steel roller assemblies. In addition, such organic plastic, corrosive-resistant materials are often less rigid and allow greater overall roller deflection when loaded than prior all metal assemblies. Such deflection upon loading can cause, in certain circumstances, greater drag and friction and consequently more binding, heat buildup and wear. Further, the prior structures have not always been well-suited to resist axial thrust exerted along the axis of the roller while also adequately rotationally supporting the roller.
Other previously known conveyor rollers have been made exclusively or predominantly from metal. Many of such structures include many openings and spaces which are very difficult to keep clean. Also, the metal itself is subject to corrosion which further reduces its desirability for sanitary applications. Use of entire stainless steel rollers and bearings is also undesirable because of the high cost and expensive machining requirements of such steel.
Some previously known roller assemblies of metal or other materials have used support inserts which move either axially or rotationally. Such supports do not adequately prevent wear, especially when the rollers are operated under load, and do not prevent or reduce contamination for sanitary purposes.
The present roller assembly was invented as an improvement over the prior known roller assemblies in order to overcome the above problems.